silverbullet-icalendar/icalendar.ts

import { clientStore, config, datastore, editor, index } from "@silverbulletmd/silverbullet/syscalls";
import { convertIcsCalendar, type IcsCalendar, type IcsEvent, type IcsDateObjects } from "ts-ics";

const VERSION = "0.3.1";
const CACHE_KEY = "icalendar:lastSync";

// Mapping of common Windows/Outlook timezones to their standard offsets (in hours)
const TIMEZONE_OFFSETS: Record<string, number> = {
  "GMT Standard Time": 0,
  "W. Europe Standard Time": 1,
  "Central Europe Standard Time": 1,
  "Romance Standard Time": 1,
  "Central European Standard Time": 1,
  "Eastern Standard Time": -5,
  "Central Standard Time": -6,
  "Mountain Standard Time": -7,
  "Pacific Standard Time": -8,
  "UTC": 0,
  "None": 0
};

// ============================================================================
// Types
// ============================================================================

type DateToString<T> = T extends Date ? string
  : T extends IcsDateObjects ? string
  : T extends object ? { [K in keyof T]: DateToString<T[K]> }
  : T extends Array<infer U> ? Array<DateToString<U>>
  : T;

interface Source {
  url: string;
  name: string | undefined;
}

interface PlugConfig {
  sources: any;
  cacheDuration: number | undefined;
  tzShift: number | undefined;
}

interface CalendarEvent extends DateToString<IcsEvent> {
  ref: string;
  tag: "ical-event";
  sourceName: string | undefined;
}

// ============================================================================
// Utility Functions
// ============================================================================

function toLocalISO(d: Date): string {
  const pad = (n: number) => String(n).padStart(2, "0");
  return d.getFullYear() +
    "-" + pad(d.getMonth() + 1) +
    "-" + pad(d.getDate()) +
    "T" + pad(d.getHours()) +
    ":" + pad(d.getMinutes()) +
    ":" + pad(d.getSeconds()) +
    "." + String(d.getMilliseconds()).padStart(3, "0");
}

function processIcsDate(obj: any, manualShift = 0): string {
  if (!obj) return "";
  let wallTimeStr = "";
  if (obj.local && typeof obj.local.date === "string") wallTimeStr = obj.local.date;
  else if (typeof obj.date === "string") wallTimeStr = obj.date;
  else if (obj.date instanceof Date) wallTimeStr = obj.date.toISOString();
  else if (obj instanceof Date) wallTimeStr = obj.toISOString();
  if (!wallTimeStr) return "";
  
  const baseDate = new Date(wallTimeStr.replace("Z", "") + "Z");
  const tzName = obj.local?.timezone || obj.timezone || "UTC";
  const sourceOffset = TIMEZONE_OFFSETS[tzName] ?? 0;
  
  const utcMillis = baseDate.getTime() - (sourceOffset * 3600000);
  const finalDate = new Date(utcMillis + (manualShift * 3600000));
  
  return toLocalISO(finalDate);
}

function isIcsDateObjects(obj: any): obj is IcsDateObjects {
  return obj && typeof obj === 'object' && ('date' in obj && 'type' in obj);
}

async function sha256Hash(str: string): Promise<string> {
  const hashBuffer = await crypto.subtle.digest("SHA-256", (new TextEncoder()).encode(str));
  return Array.from(new Uint8Array(hashBuffer)).map(b => b.toString(16).padStart(2, "0")).join("");
}

function convertDatesToStrings<T>(obj: T, hourShift = 0): DateToString<T> {
  if (obj === null || obj === undefined) return obj as DateToString<T>;
  if (isIcsDateObjects(obj)) return processIcsDate(obj, hourShift) as DateToString<T>;
  if (obj instanceof Date) return processIcsDate({ date: obj }, hourShift) as DateToString<T>;
  if (Array.isArray(obj)) return obj.map(item => convertDatesToStrings(item, hourShift)) as DateToString<T>;
  if (typeof obj === 'object') {
    const result: any = {};
    for (const key in obj) {
      if (Object.prototype.hasOwnProperty.call(obj, key)) result[key] = convertDatesToStrings((obj as any)[key], hourShift);
    }
    return result as DateToString<T>;
  }
  return obj as DateToString<T>;
}

async function getSources(): Promise<{ sources: Source[], tzShift: number }> {
  try {
    const rawConfig = await config.get<PlugConfig>("icalendar", { sources: [] });
    let sources: Source[] = [];
    let tzShift = rawConfig.tzShift ?? 0;
    let rawSources = rawConfig.sources;
    if (rawSources && typeof rawSources === "object") {
      if (rawSources.tzShift !== undefined && tzShift === 0) tzShift = rawSources.tzShift;
      if (Array.isArray(rawSources)) sources = rawSources.filter(s => s && typeof s.url === "string");
      else if (rawSources.url) sources = [rawSources];
    }
    return { sources, tzShift };
  } catch (e) {
    return { sources: [], tzShift: 0 };
  }
}

async function fetchAndParseCalendar(source: Source, hourShift = 0): Promise<CalendarEvent[]> {
  let url = source.url.trim();
  if (url.includes(" ")) url = encodeURI(url);
  const response = await fetch(url);
  if (!response.ok) throw new Error(`HTTP ${response.status}`);
  const calendar = convertIcsCalendar(undefined, await response.text());
  if (!calendar.events) return [];
  return await Promise.all(calendar.events.map(async (icsEvent: IcsEvent): Promise<CalendarEvent> => {
    const uniqueKey = `${icsEvent.start?.date || ''}${icsEvent.uid || icsEvent.summary || ''}`;
    const ref = await sha256Hash(uniqueKey);
    return convertDatesToStrings({ ...icsEvent, ref, tag: "ical-event" as const, sourceName: source.name }, hourShift);
  }));
}

// ============================================================================
// Public Commands
// ============================================================================

export async function syncCalendars() {
  try {
    const { sources, tzShift } = await getSources();
    if (sources.length === 0) return;
    await editor.flashNotification("Syncing calendars...", "info");
    const allEvents: CalendarEvent[] = [];
    for (const source of sources) {
      try {
        const events = await fetchAndParseCalendar(source, tzShift);
        allEvents.push(...events);
      } catch (err) {
        console.error(`Failed to sync ${source.name}:`, err);
      }
    }
    await index.indexObjects("$icalendar", allEvents);
    await editor.flashNotification(`Synced ${allEvents.length} events`, "info");
  } catch (err) {
    console.error("Sync failed:", err);
  }
}

export async function forceSync() {
  await clientStore.del(CACHE_KEY);
  await syncCalendars();
}

export async function clearCache() {
  if (!await editor.confirm("Clear all calendar events?")) return;
  const pageKeys = await datastore.query({ prefix: ["ridx", "$icalendar"] });
  const allKeys: any[] = [];
  for (const { key } of pageKeys) {
    allKeys.push(key);
    allKeys.push(["idx", ...key.slice(2), "$icalendar"]);
  }
  if (allKeys.length > 0) await datastore.batchDel(allKeys);
  await clientStore.del(CACHE_KEY);
  await editor.flashNotification("Calendar index cleared", "info");
}

export async function showVersion() {
  await editor.flashNotification(`iCalendar Plug ${VERSION}`, "info");
}